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Within and below Arctic sea ice exists an abundance of life. As sea ice forms, the salt water from the ocean mixes with surrounding nutrients to create and support the growth of microscopic single-celled life forms known as diatoms.
Image: A microscopic look at Nitzschia frigida.
Why this species is important
Nitzschia frigida (its scientific name) is one of the most common and important producers of food that lives in Arctic sea ice. As the sun shines through the ice during the spring months, these tiny organisms live within small channels in the sea ice. Here, they form micro-communities at the bottom of the ice. These micro-colonies supply nutrients and food to many organisms up the food chain.
The food web
The food web is an intricate chain in which all living things rely on something else to survive. The Arctic food web is one such chain.
This info graphic shows how just 1kg of a polar bear is reliant on 10kg of ringed seal. 1kg of a ringed seal's energy is based on it consuming 10kg of fish. 1kg of fish requires 10kg of zooplankton while to create 1kg of zooplankton relies on 10kg of phytoplankton.
Looking at this chain overall, to create 1kg of a polar bear requires an extraordinary 10,000kg of phytoplankton.
During the spring months, Arctic sea ice is sometimes called “dirty ice” referring to the brown colour that appears in the bottom section of the ice. As sea ice breaks up and shifts, so do the colonies of Nitzschia frigida that have been living within the ice. These visible dark spots are the remnants of the unique micro-communities that colonize the ice.
Food chain affect
Scientists are constantly examining how climate change is affecting the creation of Arctic sea ice. As temperatures rise, sea ice depletion increases. With this potential reduction in sea ice, scientists are now studying the affect this will have both on the diatom population as well as the larger Arctic food chain. Would a lack of sea ice see a reduction in the formation of Nitzschia frigida colonies and would this have an effect on the Arctic food web?
Where do they go when the ice disappears?
As Arctic waters open-up during the summer, Nitzschia frigida can be found floating in the water and sinking to the ocean bottom. How does the species get back into the ice?
Scientists are not certain why this occurs and a number of ideas have been proposed. One suggestion is that the newly formed ice in the water, near the bottom, captures microscopic cells including Nitzschia frigida. These ice crystals then rise to the surface and are incorporated into the newly forming sea-ice.
Watch this video to see freshwater diatoms on the move through a microscope.
© Video by Dr. Michael R. Gretz, Michigan Technological University.
Transcript: Freshwater diatoms
A microscopic point of view of fresh water diatoms moving in the water, there are many of them, they are moving in a linear manner. A closer point of view of diatoms moving in the water. There are two of them moving in opposite directions. A different point of view of longer diatoms moving along. A closer view of the same diatom. Another point of view of the same diatom moving a little faster across the screen. Two diatoms, moving along.